feat: full billing/FinOps surface parity across AWS, Azure, GCP

[NitinKumar004]

Goal

Keep 100% parity with how the cloud providers actually behave for cost/billing — a user should be able to fetch billing data against cloudemu exactly the way real FinOps tooling does on each cloud, across AWS, Azure, and GCP. The primary cost-query entry points shipped (AWS Cost Explorer #920, Azure Cost Management query #923, GCP Cloud Billing control-plane #922, all over the shared services/cost pricing engine); this tracks the remaining surfaces to reach full parity.

AWS

• Cost Explorer (extend feat(aws): Cost Explorer GetCostAndUsage SDK-compat handler (#173) #920): GetCostAndUsageWithResources; GetReservationCoverage / GetReservationUtilization / GetReservationPurchaseRecommendation; GetSavingsPlansUtilization / GetSavingsPlansUtilizationDetails / GetSavingsPlansCoverage / GetSavingsPlansPurchaseRecommendation; GetAnomalies / GetAnomalyMonitors / GetAnomalySubscriptions; Cost Categories (Create/Describe/List)
• AWS Budgets (budgets): CreateBudget / DescribeBudget(s) / UpdateBudget / DeleteBudget + notifications
• Savings Plans (savingsplans): DescribeSavingsPlans / DescribeSavingsPlansOfferings / CreateSavingsPlan
• Reserved Instances reporting (ec2 RI + ce coverage above)
• CUR — report definitions + S3 line-item delivery (tracked separately in feat(aws): Cost & Usage Report (CUR) — report definitions + S3 line-item delivery #941)
• Pricing (pricing): GetProducts / DescribeServices (price list)

Azure

• Cost Management (extend feat(azure): Cost Management query SDK-compat handler (#174) #923): Forecast, Dimensions, Query Exports, generateDetailedCostReport
• Consumption (Microsoft.Consumption): usageDetails (line items), budgets, reservationSummaries / reservationDetails, reservationRecommendations
• Capacity (Microsoft.Capacity): reservations / reservationOrders, reservationRecommendations
• Retail Prices API (price list)

GCP

• Detailed cost/usage: emulate the BigQuery billing export dataset (or an equivalent fetch seam) — GCP has no per-resource cost API, so real FinOps reads the export; needed for line-item parity
• Cloud Billing (extend feat(gcp): Cloud Billing SDK-compat handler (#175) #922): accounts getIamPolicy/setIamPolicy/testIamPermissions; committed-use discounts (CUDs) reporting
• Catalog pricing already partial via services/skus

Underlying

The services/cost pricing engine must model commitment discounts (Savings Plans / Reservations / CUDs) and per-service price shapes closely enough that the reservation/SP coverage & utilization numbers above are meaningful, not just zeros.